1. Field of the Invention
The present invention relates to a multi-stage switching equipment for blocking-free connection of nx input lines to nx output lines, comprising a first switching matrix network stage that includes n/2n space-division couplers, a middle switching stage that comprises x/x space-division couplers, whereby respectively one output of an n/2n space-division coupler is connected by an intermediate line to an input of a x/x space-division coupler, and comprising a third switching matrix network stage that comprises 2n/n space-division couplers, and in which a respective output of an x/x space-division coupler is connected by an intermediate line to an input of a 2n/n space-division coupler.
2. Description of the Prior Art
The primary task of switching technology is to couple inputs to outputs. In channel switching or circuit switching, the connection of inputs to outputs occurs with a switching equipment that is controlled by a switching computer. Both electro-mechanical components and electronic switches to an increasing degree are employed as contacts. Dependent on the construction of the switching equipment, signals can be transmitted via the same crosspoints in one or both directions. In addition to the standard space-division multiplex operation of switching equipment, it is also possible to realize switching equipment according to the time-division multiplex (TDM) principle or to combine the two principles.
Switching equipment are usually constructed of uniform, basic modules based on defined principles. The multi-stage Clos switching matrix network has proven particularly advantageous, this being described in the book "Neue Kommunikationsnetze" by Peter R. Gerke, Springer Verlag, 1982, in the Chapter Koppeleinrichtungen, pp. 50-51, and that is discussed in detail in the article by Clos in the Bell System Technical Journal, Vol. 32, 1953, pp. 406-424. The Clos switching matrix network contains three switching matrix network stages, whereby the couplers of the outer stages make it possible to through-connect each of the lines to a double plurality of intermediate lines (more precisely, one fewer than the double plurality) that are connected to couplers of the middle stage. A respective intermediate line extends between each of the couplers of the outer stage and of the middle stage. In larger switching equipment, however, this type of wiring results in an expense that can hardly be justified.